In recent years, a technology has been developed to realize user operation support by, for example, making a user carry out interaction operation toward a projection image which is, by using a paper document and a projector, projected on the paper document. For example, an augmented reality (AR) technology has been disclosed in which, when a user points to a word on a paper document by his/her finger, a projection image associated with the word is projected, and, when the user further points to a portion of the projection image, notes or the like associated with the word are displayed.
In the above described interface, the position of a finger of the user has to be located accurately by using a camera fixed to an arbitrary position or a camera which is freely movable. As a method to locate the position of a finger, for example, a technology has been disclosed to extract a contour of a hand by extracting a color component (may be referred to as color feature amount) of the flesh color from an imaged image and to locate the position of the finger from the contour. As a technology of image processing as described above, for example, non-patent documents such as “Survey on Skin Tone Detection using Color Spaces, C. Prema et al., International Journal of Applied Information Systems 2(2):18-26, May 2012. Published by Foundation of Computer Science, New York, USA.”, “Skin Detection—a Short Tutorial, Elgammal et al., Encyclopedia of Biometrics by Springer-Verlag Berlin Heidelberg 2009.”, “A survey of skin-color modeling and detection methods, Kakumanu et al., Pattern Recognition, Volume 40, Issue 3, March 2007, Pages 1106-1122”, and “A Survey on Pixel-Based Skin Color Detection Techniques, Vezhnevets et al., IN PROC. GRAPHICON-2003.” have been disclosed.